OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..990
Index entries for linear recurrences with constant coefficients, signature (8,21).
FORMULA
Limit_{n -> oo} a(n+1)/a(n) converges to 4 + sqrt(37).
G.f.: x*(1+7*x)/(1-8*x-21*x^2). - Stefan Steinerberger, Nov 18 2005
MATHEMATICA
LinearRecurrence[{8, 21}, {1, 15}, 20] (* Harvey P. Dale, Nov 03 2020 *)
PROG
(Magma) R<x>:=PowerSeriesRing(Integers(), 40); Coefficients(R!( (1+7*x)/(1-8*x-21*x^2) )); // G. C. Greubel, Feb 09 2023
(SageMath)
@CachedFunction
def b(n): # b = A093103
if (n<3): return (0, 1, 8)[n]
else: return 8*b(n-1) + 21*b(n-2)
def A093117(n): return b(n) + 7*b(n-1)
[A093117(n) for n in range(1, 41)] # G. C. Greubel, Feb 09 2023
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gary W. Adamson, May 21 2004
EXTENSIONS
More terms from Robert G. Wilson v, May 24 2004
Edited by Don Reble, Nov 04 2005
STATUS
approved